The C–H bending vibration v 4 of chloroform CH35Cl3

Preparation of Taraxacum kok-saghyz Rubber and Biofuel Ethanol Simultaneously by the Yeast Fermentation Process

Taraxacum kok-saghyz(TKS) rubber is considered the most ideal alternative source of natural rubber (NR). Extracting rubber from TKS with high quality, low cost, and low pollution is the basis of commercial development. The TKS roots were subjected to morphological observation and detailed compositional analysis. Scanning electron microscopy (SEM) images confirm that rubber filaments are physically entangled with plant tissues due to differences in molecular polarity. Compared with the traditional solvent TKS rubber extraction process, a new rubber extraction process developed in this study, namely, the microbial extraction (″ME″) process, is less harmful to the environment and lower in cost. The ″ME″ process is divided into three steps: dilute acid pretreatment process, enzyme degradation process, and fermentation process. After each step is completed, the purity of TKS rubber will gradually increase from 84.8% to 93.8 to 95.5%. The TKS rubber finally obtained fully meets the requirements of the traditional rubber industry, especially the tire industry. Besides, the yield of biofuel ethanol, a by-product of cellulose fermentation, reaches 2.05 g/100 g of TKS roots (dry weight), which can effectively reduce the production cost of TKS rubber. In the rubber extraction process, microorganisms have little effect on the quality of TKS rubber. The results show that the molecular weight and chemical structure of TKS rubber is very close to NR, so the ″ME″ process can be used as a new method for large-scale extraction of TKS rubber.

VIBFREQ1295: A New Database for Vibrational Frequency Calculations

High-throughput approaches for producing approximate vibrational spectral data for molecules of astrochemistry interest rely on harmonic frequency calculations using computational quantum chemistry. However, model chemistry recommendations (i.e., a level of theory and basis set pair) for these calculations are not yet available and, thus, thorough benchmarking against comprehensive benchmark databases is needed. Here, we present a new database for vibrational frequency calculations (VIBFREQ1295) storing 1295 experimental fundamental frequencies and CCSD(T)(F12*)/cc-pVDZ-F12 ab initio harmonic frequencies from 141 molecules. VIBFREQ1295's experimental data was complied through a comprehensive review of contemporary experimental data, while the ab initio data was computed here. The chemical space spanned by the molecules chosen is considered in-depth and is shown to have good representation of common organic functional groups and vibrational modes. Scaling factors are routinely used to approximate the effect of anharmonicity and convert computed harmonic frequencies to predicted fundamental frequencies. With our experimental and high-level ab initio data, we find that a single global uniform scaling factor of 0.9617(3) results in median differences of 15.9(5) cm^-1. A far superior performance with a median difference of 7.5(5) cm^-1 can be obtained, however, by using separate scaling factors (SFs) for three regions: frequencies less than 1000 cm^-1 (SF = 0.987(1)), between 1000 and 2000 cm^-1 (SF = 0.9727(6)), and above 2000 cm^-1 (SF = 0.9564(4)). This sets a lower bound for the performance that could be reliably obtained using scaling of harmonic frequency calculations to predict experimental fundamental frequencies. VIBFREQ1295's most important purpose is to provide a robust database for benchmarking the performance of any vibrational frequency calculations. VIBFREQ1295 data could also be used to train machine-learning models for the prediction of vibrational spectra and as a reference and data starting point for more detailed spectroscopic modeling of particular molecules. The database can be found as part of the Supporting Information for this paper or in the Harvard DataVerse at https://doi.org/10.7910/DVN/VLVNU7.